TrueRTA Audio Spectrum Analyzer Software

Updated: Friday, 11 January 2008

TrueRTA Self Test of a notebook PC, shown in Bar mode

TrueRTA™ is a software based audio analyzer for testing and evaluating audio systems using just a PC with basic sound capability. The instruments found in TrueRTA include:

Low distortion signal generator
Digital level meter
Crest factor meter
Dual trace oscilloscope
High-resolution real time audio spectrum analyzer

By creating these test instruments in software and employing the signal input and output capability of your PC’s sound card we are able to offer a level of performance that could only be replaced by many thousands of dollars worth of traditional test instruments. TrueRTA turns your PC into a powerful audio spectrum analyzer normally seen only in better audio research and design laboratories.

		Level - 1	Level - 2	Level - 3	Level - 4
Product Price:		1 Octave FREE!	1/3 Octave $39.95	1/6 Octave $69.95	1/24 Octave $99.95
General Product Specifications:
	Fully Adjustable Frequency Scale (10 to 50 kHz)	•	•	•	•
	Fully Adjustable dB Scale (+20 dBu to -160 dBu)	•	•	•	•
	Adjustable dB SPL Scale (+180 dB SPL to 0 dB SPL)	•	•	•	•
	Data Import	•	•	•	•
	Data Export	•	•	•	•
	Project Files Saves all Data and Notes	•	•	•	•
	Sampling Frequencies up to 96 kHz	•	•	•	•
	Prints Detailed Reports in Color and B&W	•	•	•	•
Real Time Analyzer Specifications:
To 50 kHz!	1/1 Octave Real Time Analyzer	•	•	•	•
	1/3 Octave Real Time Analyzer		•	•	•
	1/6 Octave Real Time Analyzer		•	•	•
	1/12 Octave Real Time Analyzer		•		•
	1/24 Octave Real Time Analyzer		•		•
	Cursor Readout of Data	•	•	•	•
	20 Memories which can be overlaid	•	•	•	•
	Data Utilities (Average, Smooth, Shift, Sum & Difference)	•	•	•	•
	Automatic Measurement Notes as well as your own notes	•	•	•	•
Advanced Frequency Response Measurement:
Quick Sweep (Based on a digitally generated chirp)				•	•
Signal Generator Specifications:
	Square Wave (adjustable)	•	•	•	•
	Triangle Wave	•	•	•	•
	Saw Tooth Wave	•	•	•	•
	Impulse Wave	•	•	•	•
	Sine Wave, 5 to 48 kHz	•	•	•	•
	Pink Noise	•	•	•	•
	White Noise		•		•
	Digitally Generated Sweep			•	•
Oscilloscope Specifications:
	Dual Trace 48 kHz Scope	•	•	•	•
	Freeze Display	•	•	•	•
	Measurement Notes	•	•	•	•
	One Trace Saved with each Project File	•	•	•	•
Digital Multi-Meter Specifications:
	Volts RMS	•	•	•	•
	dBu (rms and peak)		•	•	•
	Crest Factor in mV/mV			•	•
	Crest Factor in dB			•	•
	Optional Printing of the on screen meter displays	•	•	•	•
Calibration Specifications:
	Line-In and Line-Out Level Calibration	•	•	•	•
	SPL Calibration	•	•	•	•
	Relative Mode	•	•	•	•
	Microphone Calibration Files	•	•	•	•
	X-Curve / House Curve	•	•	•	•
	PC Sound System Calibration			•	•
	Digital Sweep Calibration			•	•

Here are the components that make up TrueRTA:

Audio Spectrum Analyzer

TrueRTA’s audio spectrum analyzer software shows you a detailed picture of what you’re hearing in real-time, that is, as it happens. The audio spectrum analyzer shows the changing spectrum of live input signals up to 48kHz (half the maximum sampling frequency). The size of the waveform sample is variable so that shorter samples can be used where a high frame rate is required, as in sampling live music. Longer samples provide increased low frequency resolution with the tradeoff of slower updates. The latter settings are appropriate for highly accurate frequency response measurements.

TrueRTA Audio Spectrum Analyzer in Line mode
(self test of Audigy 2 sound card)

There are a very many uses for an audio spectrum analyzer. Here are just a few:

	Observe the frequency characteristics of live music in real time.
	Observe the frequency characteristics of recorded music or other recorded audio.
	Measure the frequency response of various types of audio equipment.
	Study the noise characteristics of acoustic environments or electronic gear.
	Analyze the distortion characteristics of audio equipment.
	Use as a voice and music learning aid.
	Study the harmonic structure of musical instruments.

Some of the above applications require the use of the analyzer in combination with a test signal from the generator. Others (such as noise analysis or analyzing live or recorded music) require no test signal.

Quick Sweep

TrueRTA's Quick Sweep employs a short digitally generated sweep (chirp) to measure the frequency response of electronic and acoustical systems. Below is the measured response of a SoundBlaster Audigy 2 sound card.

TrueRTA Quick Sweep WITHOUT Sound Card Calibration
(self test of Audigy 2 card)

Below is TrueRTA with Sound System Calibration switched on. Note that the response of the sound card has been removed from the measurement so that a self test of the sound card now shows a flat response. The response of any system you now insert in the test loop can now be measured very precisely plus or minus .05 dB.

TrueRTA Quick Sweep WITH Sound Card Calibration
(self test of Audigy 2 card)

Below is a Quick Sweep measurement of a high pass filter created by inserting a .022uF capacitor in the test loop. When loaded by the input impedance of the sound card the series capacitor forms a high pass filter with -3 dB frequency at around 400 Hz. Note the total absence of any sound card response error. Only the response of the actual filter is measured when sound card correction is employed.

TrueRTA Quick Sweep of a Highpass Filter
(using sound card calibration)

	Signal Generator
TrueRTA's Signal Generator produces an ultra low-distortion sine wave variable from 5 Hz to 24kHz. The output level can be specified anywhere from full scale to a single bit of amplitude. In addition to the sine wave the generator can be switched to pink noise. The higher level versions of the product can also provide a digitally created logarithmic sine sweep from 10 Hz to 48 kHz. This signal is a high-resolution alternative to using pink noise for system testing. The swept sine wave provides a higher signal level at each frequency compared to pink noise and lacks the peaks and valleys seen in pink noise response plots. The digital Quick Sweep is an excellent alternative to stepped sine wave frequency response testing.

Oscilloscope

A screenshot of TrueRTA in Oscilloscope mode

TrueRTA's Oscilloscope allows you to view the input signal waveform.

	0.5 V per division down to 0.001 V per Division.
	Time base ranges from 20mSec/Division down to 0.05mSec/Div.
	Traces can be triggered from either the Left or Right inputs.
	Trace can be frozen at any time by pressing the space bar.
	Background and trace colors for the scope display can be switched among 5 different color schemes.
	All controls are conveniently available at both the scope menu and at the detachable control bar.

Oscilloscope View of Captured Quick Sweep Waveform

Digital Voltmeter

TrueRTA's Digital Voltmeter can be calibrated for your sound card. You will need a digital voltmeter of your own so that you can measure the signal level. Then, enter that value and TrueRTA will be calibrated for your sound card, allowing precise measurement of input signals. The meter can display any or all of the following:

	Level in millivolts
	Level in dBu (.775 V reference)
	Crest Factor in mV/mV (ratio of peak to rms level)
	Crest Factor in dB

Selected functions are displayed in the same window as the oscilloscope or spectrum analyzer display.

Additional Information:

System Requirements:

The minimum requirements to use TrueRTA are a PC with a 500 MHz Pentium III processor, 64MB RAM and full duplex 16 bit sound capability. (TrueRTA’s default calibration is for the popular Sound Blaster Audigy 2 sound card from Creative Labs, Inc.) Unlike most other software applications TrueRTA can easily demand every bit of processing power your computer can provide. For this reason it is recommended that you not have any other applications running in the background when you are running TrueRTA.

Besides TrueRTA what else do I need to set up an audio test system?

Our FAQ page has information on microphones and other gear you'll need.

About the TrueRTA Download:

When you download the FREE version of TrueRTA and then decide to upgrade to a more powerful level, just go to the catalog, select the level you want and submit the order. We will email you a Registration Code. After you receive the code, look under the Help menu and locate User Registration. Enter the code in the appropriate Level field. Upon successful entry of the code you will have an immediate upgrade to the level you ordered. Menu items will be activated, providing greater power. No need to download the file again.

Order TrueRTA!

387 Duncan Lane
Andersonville TN 37705

Phone/Fax: 865-494-3388


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